1. Technical Field of the Invention
The present invention relates to the processing of signals delivered by a matrix of pixels of an image sensor.
2. Description of Related Art
An image sensor conventionally comprises a matrix of pixels. Each pixel delivers an electrical signal whose level depends on the quantity of light received by the pixel. This signal is conventionally stored in a pair of sampling capacitors then it is amplified in a read amplifier.
Currently, the circuits of systems for reading signals delivered by a pixel use a 0.34 μm technology with double-oxide transistors, supplied by 3.3 V. These transistors possess an acceptable operating dynamic range and gain.
Nevertheless, the appearance of new submicron technologies, for example a circuit using 0.18 μm technology, implies the use of single-oxide transistors with lower and lower supply voltages. As a result, the operating dynamic range is relatively limited since very little margin is left for the maximum signal attainable by the pixel.
A need accordingly exists to provide a solution to this problem.
Embodiments of the present invention propose a new reading system allowing a part of the dynamic range to be recovered and the gain to be increased for image sensors. The invention can be applied to pixels that use either double-oxide transistors or new submicron technologies, for example 0.18 μm, using thin-oxide (or single-oxide) transistors.